Excluded failing WordPress 5.6 core tests from vip-go-mu-plugins CircleCI workflow

We have a couple of CircleCI jobs that run core tests with vip-go-mu-plugins attached for each submitted change. Sometimes vip-go-mu-plugins ends up changing assertions in a core test and those tests need to be excluded since we know they will fail 100% of the time.

https://github.com/Automattic/vip-go-mu-plugins/pull/1909